Ten patients with tuberculous enterocolitis were diagnosed colonoscopically. In four, the diagnosis was confirmed by positive acid fast stain or the presence of caseating granuloma in colonic biopsy material or ileal washings. In one other patient a cervical lymph gland revealed acid-fast bacilli. He was the only patient with extraintestinal disease, indicating that primary tuberculous colitis is probably more common than secondary in Saudi Arabia. In the other five patients the colonoscopic diagnosis was confirmed by a complete response to antituberculous triple therapy. Six patients had hypertrophic, two ulcerohypertrophic and two widespread ulcerative lesions. Colonoscopy with biopsies has definite advantages over barium enema in diagnosis. After thus excluding malignancy, Crohn's disease remains the most important differential diagnosis. A ten-week therapeutic trial of antituberculous treatment is recommended in patients from high-risk populations with a typical history and colonoscopic picture to avoid the morbidity and mortality of diagnostic laparotomy.